Later

Later is a lean Redis-backed event scheduling library for Ruby.

Usage

Later allows you to set unique events on a schedule and run them in the future:

require 'later'

schedule = Later[:schedule]
schedule.set 'event-1', Time.now + 60
schedule.set 'event-2', Time.now + 120
schedule.set 'event-3', Time.now + 180

Rescheduling an event is simple:

schedule.set 'event-1', Time.now + 240

And an event can unset with equal ease:

schedule.unset 'event-1'

You can manage multiple schedules using different keys:

reservations = Later[:reservations]
appointments = Later[:appointments]

The schedules are stored on the default Redis instance. If you need a schedule which must reside on a different Redis instance, you can pass a Nest object when referencing a schedule set.

redis = Redis.new host: host, port: port
key = Nest.new 'Reservations', redis

reservations = Later[key]

Workers

Workers are Ruby processes that run forever. They allow you to process event schedules in the background:

require 'later'

Later[:schedule].each do |event|
  # Do something with the event.
end

# This line is never reached.

Timeouts, Blocking & Polling

Later::Schedule#each accepts an optional timeout parameter, which has a default value of 1. Passing an Integer will use Redis' blocking mechanism to process the schedule and is therefore more efficient. Passing a Float will poll Redis using the given timeout, and should only be used for events which need to be triggered with millisecond precision.

See BLPOP and BRPOPLPUSH for more information.

The below schedule will be polled every 0.1 seconds:

Later[:schedule].each(0.1) do |event|
  # Do something with the event.
end

Stopping

If for some reason, a worker has to stop itself from running:

Later[:schedule].each do |event|
  # Do something with the event.

  Later[:schedule].stop! if stop?
end

# This line is reached when stop? is true and Later[:reservations].stop! is called.

Installation

Add this line to your application's Gemfile:

gem 'later'

And then execute:

$ bundle

Or install it yourself as:

$ gem install later

Contributing

1. Fork it
2. Create your feature branch ( git checkout -b my-new-feature )
3. Create tests and make them pass ( rake test )
4. Commit your changes ( git commit -am 'Added some feature' )
5. Push to the branch ( git push origin my-new-feature )
6. Create a new Pull Request